1. Field of the Invention
The present invention relates to a pressure atomizing oil burner, which atomizes light fuel of low viscosity (below 12 centistoke at 20.degree. C.) below the coking and cracking temperature of crackable components, as well as to processes for operating the oil burner.
2. Description of the Prior Art
Conventional oil burners frequently use the pressure atomizing principle. In this case the fuel oil is supplied to the pressure atomizing nozzle by a pump at a pressure of 10-14 bar. This pressure atomizing nozzle has a swirl chamber into which the fuel is fed by tangential channels so that it rotates in the swirl chamber an leaves it as an atomizing oil film.
For this kind of atomizing and only when using heavy or medium fuel of high viscosity, it has been usual to preheat the fuel before atomization in order to reduce viscosity and to make pressure atomization possible at all. For oil burners of the above-mentioned kind which burn light and superlight fuel oil, this preheating has not been necessary since light fuel oil has, at room temperatures, substantially lower viscosity than considerably preheated medium or heavy fuel and its use for operating the conventional relatively powerful pressure atomizers has been satisfactory. The desired burner capacity is determined by the size of the atomization nozzle. Especially in the case of low burner capacities which have only lately been requested and whose flow rate is less than 2 kg/h, difficulties concerning the quality of combustion and reliability have risen. These difficulties are due to the necessarily small cross-section of the nozzles used, since these nozzles may easily cause problems due to solid components of the fuel that may deposit at the inside walls of the outlet. The necessarily small cross-sections of the nozzles show a strong tendency to deterioration in atomization which could not completely be counter-balanced in spite of considerable pressure increase. In June 1977 these difficulties were still discussed in the German technical journal "Ol- und Gasfeuerung", for example, and it was decided that oil burners operated by the pressure atomizer process were not possible for low capacities and that different burning techniques by means of supersonics and the like, would have to be applied.
Different kinds of oil burners the gas atomizers could not help in overcoming the above-mentioned difficulties. Gas atomizers are known which preheat the fuel oil to temperatures of over 300.degree. C. before combustion in order to achieve evaporation and stoichiometric combustion. For such vaporizing gas burners very expensive and powerful heating devices are necessary. The essential disadvantage, however, is the fact that the fuel oil must be heated to a far higher temperature than the coking or cracking temperature which is usually about 150.degree. C. The thus produced tailings clog the heating device and occasionally the nozzle as well, so that this kind of oil burner cannot overcome the above-mentioned disadvantages, either.